1. Field of the Invention
The present invention relates to apparatus for purifying contaminated liquids and more particularly to apparatus for electrochemical purification of contaminated liquids.
The invention may be employed for purifying liquids contaminated with organic substances, mechanical suspensions, surfactants, and the like.
The invention is particularly useful for purifying liquids contaminated with polymers and petroleum products, such as waste waters containing oils and greases.
2. Description of the Prior Art
Of all the known devices for purifying contaminated liquids, the widest and ever increasing application has recently been found by apparatus for electrochemical purification of liquids, in particular those where liquid is purified by the electroflotation and electrocoagulation methods, which is due to their high performance capabilities.
Known in the art are apparatus where the process of electrochemical purification of contaminated liquid is accomplished either periodically, i.e. in batches, or continuously. The latter appear to be more promising. Such apparatus ordinarily comprise a settling chamber communicating with an electroflotation or an electrocoagulation chamber where electrodes are disposed. The apparatus comprising an electrocoagulation chamber with soluble electrodes, wherein also the flotation is accomplished, will be discussed hereinafter. The highest economic efficiency and purification rate are characteristic of those apparatus wherein the contaminated liquid is mixed with the electrode dissolution products in the electrocoagulation chamber above the electrodes, since this prevents fouling of the electrode surface by impurities contained in the contaminated liquid. Thus, an apparatus for electrochemical purification of waste waters (USSR Inventor's Certificate No. 644,738) comprises a settling chamber with outlet pipe to discharge purified liquid; said settling chamber communicates with an electrocoagulation chamber installed therewithin and having in its bottom part a system of soluble electrodes and an inlet pipe to feed electrolyte.
This apparatus suffers from a serious disadvantage consisting in that a portion of the sludge forming in the purification of a contaminated liquid settles to the bottom part of the electrocoagulation chamber, fouling the electrodes and clogging the interelectrode space and the inlet pipe to feed electrolyte. Moreover, the aggregates of hydroxides of the soluble electrode metal, contained in the sludge, may cause a short-circuit across the electrodes, which greatly impairs the operational dependability of the apparatus. Also, an intense fouling of the electrocoagulation chamber electrodes occurs at accidental interruptions in the electrolyte feed (such as in the event of a failure of the pump feeding the electrolyte). The above disadvantages, apart from impairing the operational dependability of the apparatus, lead also to a higher consumption of the electrodes and electric power in purifying contaminated liquids.